The aim of this project is to examine the involvement of certain ribonucleases in cellular events. The scope of this project has evolved to include protein chemistry, enzymatic activity, overproduction of proteins and the consequences of changes in the level of enzymatic activity within the cell. In particular, ribonucleases specific for RNA of RNA-DNA hybrids are being examined for their functional role within the cell. Multiple enzymes exhibiting RNase H activity have been reported within cells and our experiments are aimed at understanding the need for multiple forms of the enzyme and what effects there would be upon inhibition of each (or all) of the RNase H activities. This is particularly relevant since the AIDS virus requires the functioning of its own RNase H to be infectious.